GLOSSARY

of River Terminology

A brief introduction to some of the terms used on this web site.

Agricultural Area Supported

geographical area of agricultural activity within the river catchment area

Anabranch

a section of a river or stream that diverts from the main watercourse channel (or mainstem) and rejoins the mainstem downstream.In
the simplest case, an island or rock in the river creates a main course
and an anabranch course; a more significant anabranch would diverge for
a distance of several kilometres before rejoining. River deltas
branch into large numbers of courses, though these are not normally
regarded as anabranches, as the net result is usually multiple
discharge points rather than a rejoined unified flow.

Catchment (Drainage) Area

the area draining into a river or tributary

Delta

a deposit of soil, usually triangular, formed at the mouth of some rivers

Earliest Human Settlement

earliest archaeological evidence of human settlement

Human Population Supported.

numbers of humans resident within the catchment area

Industrial Area Supported

geographical area of industrial activity within the river catchment area

Length

distance from source to mouth, following the route of the water

Mainstem

the
principal river within a given drainage basin, in the case where a
number of tributaries discharge into a larger watercourse. Viewed in
terms of the Strahler Stream Order system, the mainstem would be the
highest order stream amongst the streams in a given drainage basin. The
United States National Weather Service considers the mainstem as the
principal object of flood forecasting. In detailed analyses of riverine
hydrology, mainstem also refers to precise channel mapping of the
principal drainage; for example, in a braided channel or system with
anabranch elements the mainstem is designated as the principal braid or
channel within the overall river.

Rain Forest Area Supported

geographical area of rain forest within the river catchment area

Source

the point from which a river springs

Strahler Stream Order

The
Strahler Stream Order is a simple hydrology algorithm used to define
stream size based on a hierarchy of its tributaries. The streams range
from one at the headwaters (which is a "1") to the most powerful which
is the Amazon River which is a "12." The Ohio River is an "8" and the
Mississippi River is a "10." 80 percent of the streams and rivers on
the planet are first or second order.

To qualify as a stream
it must be perennial. When two first-order streams come together, they
form a second-order stream. When two second-order streams come
together, they form a third-order stream. Streams of lower order
joining a higher order stream do not change the order of the higher
stream. Thus, if a first-order stream joins a second-order stream, it
remains a second-order stream. It is not until a second-order stream
combines with another second-order stream that it becomes a third-order
stream. It is important to appreciate that stream order is dependent
upon map scale. As scale decreases and more detail is added to the
river network (i.e. new tributaries) then a river may increase its
stream order.

Arthur Newell Strahler first proposed the
hierarchy in 1952 in an article “Dynamic basis of geomorphology,” in
the Geological Society of America Bulletin. It is often referenced in
professional descriptions of rivers as Strahler 1952.

Tributary

a
stream or river which flows into a mainstem (or parent) river, and
which does not flow directly into a sea. In orography, tributaries are
ordered from those nearest to the source of the river to those nearest
to the mouth of the river. A confluence is where two or more
tributaries or rivers flow together. The descriptive terms right
tributary and left tributary always apply from the perspective of
looking downstream (in the direction the is going), similarly to the
river banks. The opposite of a tributary is a distributary; a
river branch that flows away from the main stream. A river and all its
tributaries drain the watershed of the river.

Urban Area Supported

geographical area of urban conurbation within the river catchment area

Volume

cubic capacity of amount of water considered to be in the river at any one time or discharging from the mouth

Weight

weight of amount of water considered to be in the river at any one time or discharging from the mouth